Universe

The universe is not stranger than humans can imagine, but stranger than humans can imagine. Astronomers and theoretical physicists re-prove this adage with disturbing regularity. Where it was once thought that speed of light was an upper limit that nothing could reach, much exceed, they discovered the existence of particles that could not move slower than light. It is also explained that the universe is uncounted billions of expanding light years across and would take billions of years to cross even if we could travel at light speed. However, there might be shortcuts through all that space by way of stellar "wormholes" or some such.[1] Other forms of travel through the universe may involve entering the past through time travel.

All of the various alternate universes, parallel worlds, and dimensions make up the multiverse.